Screen printing machine with oval rail for indexing pallets

ABSTRACT

This disclosure is directed to a screen printing machine having an oval track or rail about which a series of pallets supporting a work piece are indexed from station to station. The arrangement is such that the pallets travelling about the oval rail are always disposed or maintained in a common plane. A printing head assembly having one or more color stations is operatively associated for movement into and out of printing relationship with one or more of the pallets as the pallets are indexed and maintained in a common plane.

PROBLEM AND PRIOR ART

Heretofore in pallet screen printing machines the pallets wereoperatively connected to a conveyor means or driving chain so thatpallets traveled on an endless path in spaced upper and lower flights.As a result, relatively complex structure was required at the respectiveends of the endless conveyor or driving chains to maintain therespective pallets horizontal as they rounded the ends of the conveyoror chain in moving about the endless path. It has also been observedthat the returning pallets travelling along the lower flight of theendless conveyor were rendered virtually inoperative as an operatingstation. For this reason twice as many pallets were required than wereotherwise necessary for economically performing a printing operationbecause the returning pallets along the lower flight could not bepractically utilized. Therefore the known pallet machines requiredcostly and complex structure, resulting in greatly increased overallcosts without any increase in production. Also such machines required aconsiderable amount of floor space.

OBJECTS

An object of this invention is to provide a screen printing machinehaving a minimum number of pallets travelling in a common plane wherebythe rate of production can be maintained comparable to machines havingtwice the number of pallets travelling in endless superposed flights.

Another object is to provide a pallet screen printing machine which isrelatively simple in construction, inexpensive to fabricate, and whichis positive in operation.

Another object is to provide a screen printing machine having a seriesof pallets moving in a common plane about an endless oval path.

Another object is to provide a pallet screen printing machine whereinone or more color printings of a workpiece can be attained.

Another object is to provide a pallet screen printing machine having.Iadd.a .Iaddend.printing head extending over one or more of a pluralityof pallets travelling in a common plane about an endless path.

BRIEF SUMMARY OF THE INVENTION

The foregoing objects and other features and advantages of thisinvention are attained by a supporting frame means having mountedthereon an oval rail or track wherein the plane of the oval rail ishorizontally disposed. A plurality of pallets are circumferentiallyspaced about the oval rail and they are interconnected by a flexibledrive member by which they are indexed about the rail from station tostation.

A printing head assembly is pivotally connected on the frame means tooverlie one or more of the pallets and is mounted for movement between aprinting and non-printing position relative to the one or more pallets.The printing head includes a head frame for supporting a printing screenin position relative to a workpiece to be printed supported on thepallets. A squeegee carriage carrying a squeegee and a flood bar ismovably mounted on the head frame for transversing a printing strokewhen the head assembly is disposed in an operative printing position anda flood stroke when the head assembly is in the inoperative non-printingposition. The printing screen is supported in a screen holder which isoperatively connected to the head frame to provide for limited lostmotion therebetween as the printing head assembly is moved betweenoperative and inoperative positions.

Operatively connected to the head frame of the head assembly are one ormore locating bars which are cooperatively associated with the palletsso as to insure proper registration of the pallets when the printinghead assembly is disposed in printing position.

The drive means for the respective pallets includes the flexible drivemember which is suitably threaded about a sprocket journalled on a maindrive shaft which is coupled in driving relationship to a drive motor.Operatively associated with the drive means is an indexing means in theform of a ram stop and cooperating cam follower which operates to effectan intermittent indexing of the respective pallets from station tostation during machine operation.

FEATURES

A feature of this invention resides in the provision of a screenprinting machine having a plurality of pallets travelling in a commonplane about an oval rail and having a printing head assembly mounted formovement between a printing and non-printing position cooperativelyassociated with one or more of the respective pallets.

Another feature of this invention resides in the provision of an ovaltrack pallet screen printing machine having a movable printing headassembly and locating means operatively associated therewith foreffecting proper registration of the pallets in the printing position ofthe head assembly.

Another feature of this invention resides in the provision of a palletscreen printing machine constructed so as to provide for maximumproduction with the use of a minimum number of pallets.

Another feature resides in the provision of a screen printing machinehaving a plurality of pallets arranged to be indexed in a common planeabout an endless path and having a pivoting printing head assemblyarranged to be moved into and out of printing relationship with one ormore of the pallets in a printing station and having cooperativelyassociated therewith locating means to insure proper registration of thepallets in printing position.

Another feature of this invention reside in the provision of a drivemechanism operatively associated with an indexing means to provideintermittent movement of the respective pallets about the oval rail.

Other features and advantages will become more readily apparent whenconsidered in view of the drawing and following detailed description inwhich:

FIG. 1 is a generally diagrammatical plan or top view of a screenprinting machine embodying the present invention in which the printinghead assembly has been omitted.

FIG. 2 is an end elevation view of FIG. 1 in which the printing headassembly is diagrammatically illustrated.

FIG. 3 is a detailed bottom plan view of a pallet construction utilizedin the screen printing machine of FIGS. 1 and 2.

FIG. 4 is a sectional view taken along line 4--4 on FIG. 3.

FIG. 5 is a detailed side elevation view of a fragmentary portion of thescreen printing machine of FIGS. 1 and 2 in the solid line showingillustrating the printing head assembly in the operative printingposition and in an inoperative non-printing position as indicated by thedotted line showing thereof.

FIG. 6 is a plan view of the printing head assembly of FIG. 5.

FIG. 7 is an enlarged detailed elevational view illustrating the driveand indexing means of the screen printing machine of FIGS. 1 and 2.

FIG. 8 is a plan view of the drive and indexing mechanism of FIG. 7.

FIG. 9 is a schematic diagram of the control circuit for sequencing theoperating components of the machine.

Referring to the drawing there is shown therein a screen printingmachine 20 which is particularly adapted for screen printing a pluralityof separate and distinct articles, as for example, T shirts, towels,posters and the like. An important feature of the machine 20 is that theworkpiece W to be printed is intermittently indexed from station tostation about an oval track or rail 25 in which the workpieces arealways maintained in a common horizontal plane as they are moved fromstation to station. As seen in FIGS. 1, 2, 5 and 6, the screen printingapparatus 20 embodying the present invention comprises a supportingframe means 21 comprised essentially of rectangularly disposed supportlegs 22 which are interconnected by longitudinally and transverselyextending structural frame members 23 and 24. Mounted on top of thesupport frame structure 21 on suitable rail support members 26 is anoval track or rail 25. As best seen in FIG. 1 the oval track or rail 25is defined by a tubular member having opposed substantially parallelside rail sections 25A-25A interconnected at the opposite ends thereofby a curved track section 25B. The rail sections 25A, 25B thus define asubstantially oval shaped track or rail 25 which extends substantiallythe longitudinal length of the frame along one side thereof and whereinthe plane of the oval track 25 is substantially horizontally disposed.

A plurality of work supporting pallet means 27 are spaced about the ovalrail 25. As best seen in FIGS. 3 and 4 each of the respective palletmeans 27 comprises a base plate 28 which has connected to theundersurface thereof a subplate 29. Rotatably journalled to the subplate29 are two pair of opposed guide rollers 30-30 and 31-31 arranged tostraddle therebetween the tubular rail or track 25 whereby therespective pallets are maintained in rolling engagement with the track.As noted the rollers are flanged to compass the rail 25 and therebysupport the pallet thereon.

Detachably secured to the pallet base plate 28 is a work support plate32. The work support plate 32 is slidably mounted on the pallet baseplate 28 so that the work support plate 32 can be readily interchangeddepending upon the nature and size of the workpiece W to be printed.Suitable latching means are provided for securing the work support plate32 to the pallet base plate 28. In the illustrated form of the inventionas best seen in FIG. 3, the latching means for detachably securing thework support plate 32 comprises a pair of hook and eye fasteners 33which are maintained under spring tension, by means of latching springs34 secured at one end to the side of the base plate 28. Accordingly thearrangement is such that by effecting disengagement of the hook and eyefastener 33, the work support plate 32 can be rendered readily removedwith respect to the pallet base plate 28. As seen in FIGS. 1 and 2respective pallets 27 are supported on the guide rail or track so as toextend outwardly therefrom. The free end of the respective pallet baseplate 29 is provided with an extended reduced end portion 28A which hasformed therein a notch 34 to accommodate a locating bar 35 to effectproper registration of the respective pallets 27 in the printingposition as will be hereinafter described. As best seen in FIGS. 1 and 2the oval track 25 enables the respective pallets 27 to be maintained ina common horizontal plane as they are indexed from station to stationthroughout the operating cycle of the machine as will be hereinafterdescribed.

The respective pallet means are interconnected by a flexible drivemember 36 so that the individual pallets 27 may be indexed in unisonabout the endless rail or track 25. In the illustrated form of theinvention the flexible interconnecting drive member comprises a chain 36of the like which is suitably threaded about end sprockets 37 and 38 orpulleys which are rotatably journalled adjacent the opposed curvedsections 25B, 25B of the oval track 25. Sprocket 37 is journalled abouta jack shaft .[.38.]. .Iadd.39 .Iaddend.suitably supported adjacent oneend of the track 25. The other or driving sprocket 38 is journalled to amain drive shaft 40 which is rotatably supported in upper and lowerbearings 41 mounted on the supporting frame structure of the machine asbest seen in FIGS. 7 and 8. The arrangement is such that the flexibledrive chain 36 interconnecting the respective pallets are suitablydisposed in meshing relationship about the end sprockets 37 and 38 toeffect the drive of the pallets about the rail 25.

The drive means for driving the chain 36 comprises a motor means 42which is mounted to one side of the main drive shaft 40 on suitablebracket 43. In the illustrated form of the invention motor means 42 isillustrated as a fluid motor. However, it will be understood that othertypes of motor means may be utilized for effecting the drive of therespective pallets about the oval rail 25.

The output shaft 44 of the motor means 42 has connected thereto asprocket 45 which is operatively connected in driving relationship by aflexible drive or chain 46 to a driven sprocket 47 journalled to themain drive shaft 40. It will be understood that whenever the motor means42 is energized, drive sprocket 38 is driven in response thereto throughthe drive couplings 45, 46 and 47.

Connected to the lower end of the main drive shaft 40 to rotatetherewith is a deceleration cam 48 which is adapted to be operativelyassociated with a suitable control, as for example, a microswitch 49which is connected in the control circuit to effect a deceleration ofthe moving parts of the apparatus as will be hereinafter described.

An indexing means 50 is operatively associated with the motor drivemeans 42 so as to permit intermittent movement or drive of therespective pallets from station to station during machine operation. Asbest seen in FIGS. 7 and 8 the indexing means 50 comprises a ram stoplever 51 which is pivotally mounted at one end about a pivot 52 mountedon the machine supporting structure 21. An actuating means 53 in theform of a piston and cylinder assembly is operatively associated withthe lever 51 to effect the movement thereof between operative andinoperative positions as seen in FIG. 8. The cylinder portion 53A ofassembly 53 is pivotally mounted to a suitable bracket 54 mounted on amachine frame. The piston rod 53B of the piston and cylinder assembly 53in turn is pivotally mounted to an intermediate portion of the ram stoplever 51. A cam follower stop 55 is connected to the driven sprocket 47so that in operation whenever the ram stop lever 51 is disposed in anoperative position as indicated in position A in FIG. 8, the ram stoplever is disposed so as to engage the cam stop follower 55 to prohibitrotation of the driven sprocket 47 and the drive of the pallets. Whenthe piston and cylinder assembly 53 is actuated to extend the piston toa position B as indicated in FIG. 8, the ram stop lever 51 is moved awayfrom the cam stop follower 55 thereby permitting the drive of thepallets to be actuated to advance the pallets 27 to the next succeedingstation. The arrangement is such that after the driving sprocket 47 andpallets driven thereby have advanced a predetermined amount, thedeceleration cam 48 actuates the microswitch 49 controlling throughsuitable valves the fluid to the fluid motor to effect a predetermineddeceleration of the driving motor. As will be hereinafter described thecontrol and operation of the motor drive means 42 is such as to effectan intermittent advance of the respective pallets from station tostation in accordance with a predetermined sequence or operating cycle.

In the illustrated form of the invention the fluid for activating thefluid drive motor 42 is contained in a reservoir or tank T mounted onthe frame structure. Operatively connected to the source of fluid, e.g.,hydraulic fluid, is a drive pump P which is operated by an electricmotor 56.

To effect automatic screen printing of the workpiece W supported on therespective pallets, a printing head assembly 60 is mounted on thesupporting frame structure 21 for movement between an operative, loweredprinting position and an inoperative, raised, non-printing position. Asbest seen in FIGS. 5 and 6 the printing head assembly 60 comprises aprinting head frame 61 which is pivotally mounted on the support framestructure 21 to pivot about pivot 62. The printing head frame 61comprises a pair of opposed upright members 61A mounted to pivot about62. Connected to the upper end of each of the pivoting uprights 61A-61Ais a laterally extending side rail 61B, 61B. As best seen in FIGS. 5 and6 the side rails 61B, 61B are disposed to extend to one side of the ovalrail or track 25 and overlie one or more pallets 27. Mounted on therespective side rails 61B, 61B of the headframe is a squeegee carriagemeans 70. The carriage means comprises opposed carriage bodies 71-71having journalled thereon guide rollers 72 arranged to straddle therespective side rails 61B to permit the carriage 70 to be in rollingengagement with the side rails 61B-61B. A transversely extendingsqueegee support bar 73 and a flood support bar 74 interconnect therespective carriage bodies. Spaced along the squeegee support bar 74 areone or more squeegees 75, depending upon the number of printing screensbeing used. Each squeegee 75 is adapted to be disposed in contact withan associated printing screen 76 to force the color therethrough duringa screen printing operation. If desired one or more flooding parts 77may be suspended from the flood support bar 74. As best seen in FIG. 5the flood bar 77 is supported by a holder 78 which is normally biased bya spring 79 toward the printing screen 76. Interconnecting therespective flood bar holders is a cross bar 80 which has journalled tothe ends thereof guide rollers 81. As best seen in FIG. 6 the respectiveguide rollers or wheels 81 are arranged to be disposed in rollingengagement with a bridge member 82 which extends transversely of theprinting head along the opposed ends thereof. The arrangement is suchthat in the printing position of the apparatus, as seen in FIG. 5, therolling engagement of the roller 81 on the bridge member is such as tocompress or bias the flood bar spring 79 whereby the flood bars arespaced above the printing screen during the printing stroke of thesqueegees 75.

A printing screen holder 85 is supported below the printing head frame60 so as to provide for limited lost motion between the screen 76 andthe squeegee 75 as the printing head 60 is moved between a printing andnon-printing position. As best seen in FIG. 5, screen holder 85comprises a rectangular frame structure 86 which is pivotally connectedat one end to the support frame structure 21 of the machine about pivot88. The other longitudinal side of the screen holder 85 is dependentlysupported by a connecting rod 87 from the free end of the head frameside rails 61B-61B. As seen in FIG. 5, a pair of spaced stops 87A, 87Bare adjustably mounted on the connecting rod 87. The arrangement is suchthat as the printing head frame 60 is pivoted from a lowered operativeposition to a raised inoperative position, as seen in FIG. 5, thesqueegee 75, which is fixed relative to the printing head frame 61, willmove off the screen before the screen is caused to be lifted. This isattained by the spacing between the limit stops 87A, 87B connected tothe connecting rod or link 87. In operation the printing head assembly60 as it is initially moved to a raised inoperative position, asindicated by the dash dot line of FIG. 5, will effect the lifting of thefront end of the screen 76 only after the squeegee 75 has been raisedand when the lower limit stop 87B has engaged the screen holder 85.Continued movement of the head assembly 60 to its inoperative positioncauses the screen to pivot about pivot 88. In doing so, the floodrollers 81 are raised off the bridge member 82 whereby the tension ofthe flood spring 79 will cause the flood bar 77 to be lowered intoengagement with the printing screen 76 to effect a flood stroke on thereturn of the squeegee carriage to its initial operating position.

A drive means 90 is provided for affecting the transversing stroke ofthe squeegee carriage to effect the printing and flooding strokes. Asbest seen in FIG. 6, the squeegee carriage drive means 90 comprises amotor, e.g., a reversible fluid motor 91 which is connected in drivingrelationship to a carriage drive shaft 92 extending transversely betweenthe upright members 61A-61A of the printing head frame 60. Connected tothe ends of the carriage drive shaft 92 is an end sprocket 93-93 aboutwhich a flexible drive means, as for example a chain 94 or the like, isthreaded. The other end of the endless drive chain 94 is threaded aboutan idler sprocket 95 rotatably journalled on the forward end of theopposed rails 61B-61B. The respective driving chains 94 are operativelyconnected to the carriage bodies 71 so that rotation of the drive shaft92 in one direction or the other will effect a reciprocation of thesqueegee carriage bodies 71 and associated squeegee bar and flood bartransversely of the printing screen to alternately effect the printingand flooding stroke during the machine cycle of operation.

To effect a proper registration of the respective pallets when they havebeen indexed to the screen printing station beneath the printing headassembly 60, a registration means 97 is cooperatively associated withthe printing head assembly .[.20.]. .Iadd.60 .Iaddend.to effectregistration of the pallet with the printing screen. As best seen inFIG. 5 the registration means 97 comprises a locating bar 35 which ispivotally mounted to the machine frame about pivot 98 fixed to thesupporting structure. A connecting link 99 interconnects the locatingbar 35 with the pivoting uprights 61A of the head frame 60. Thearrangement is such that whenever the printing head 60 is disposed in anoperative printing position, the locating bar 35 is pivoted so that itsupper end 35A engages the registration notch 34 formed in the extendedend of the pallet .Iadd.base plate 28. .Iaddend.Whenever the printinghead 60 is moved out of printing position or to a raised position asindicated in FIG. 5, the locating bar is pivoted away from the pallet toeffect disengagement thereof from the registering notch 34 and enablingthe pallets to be indexed to the next succeeding position. It will beunderstood that one or more locating bars are coupled to operate inunison depending upon the number of pallets that are being printed. Alsothe printing head 60 may be sized to hold one or more screens dependingupon the number of colors being printed.

As seen in FIG. 5, an actuating means in the form of a piston andcylinder assembly 100 is provided for effecting the actuation of theprinting head 60 between a printing and non-printing position. Asillustrated, the cylinder 100A of the actuating means 100 is pivotallyconnected to a suitable support 101 mounted on the support structureabout pivot 102. The piston rod 100B of the assembly 100, is pivotallyconnected to the pivoting upright 61A of the head assembly about pivot103. Accordingly.Iadd., .Iaddend.whenever the piston and cylinderassembly 100 is actuated, the printing head is pivoted between anoperative printing position and an inoperative non-printing positionwith the registration means 97 responding accordingly.

With the arrangement described it will be apparent that the respectivepallets 27 are disposed in a horizontal plane whereby they are indexedand maintained in a common plane at all times. Thus the respectivepallets 27 are exposed so that each is rendered readily usable as anoperating station; thereby providing a minimum number of pallets for agiven machine without adversely affecting the production and/or speed ofoperation.

In the illustrated form of the invention eight such pallets areillustrated whereby the pallets at two stations, as for example stations27A and 27B may be utilized for loading the workpiece thereat andwhereby the next four succeeding pallets located at the printingstations 27C-27F may effect a four color printing of the workpiece, andwhereby the other two pallets located at stations 27G and 27H may beutilized to effect the removal of the workpiece therefrom. By providinga machine with a minimum number of pallets, the overall size andstructure of the machine is greatly reduced, and thereby results in amaximum saving of initial capital expenditure. The machine describedenables maximum production with a minimal amount of effort, capital andlabor. Because of the proximity of the feeding stations 27A, 27B andtake off stations 27G and 27H disposed on the same side of the machine,the arrangement is such that it can be operated at reasonable speed by asingle operator. Also the apparatus enables the printing to beaccomplished with one or more colors in a readily simple, efficient andexpedient manner wherein all the printing is performed on the same sideof the machine to further simplify the machine structure and wherein thefeeding and unloading of the machine can be readily effected on theopposite side of the machine.

To support the free end of the pallets 27 in the printing stations ofthe machine, a support rail 104 is provided. As best seen in FIG. 5, thesupport rail 104 extends along the machine frame structure so as tosupport the reduced end portion 28A of the respective pallets 27 whenthe pallets have been indexed into the printing position beneath theprinting head 60.

FIG. 9 illustrates a schematic diagram of the control circuit 105 bywhich the component parts of the machine are sequenced during themachine operating cycle. As shown the fluid pump P for maintaining fluidpressure is activated by an electric motor 56. Connected in parallel tothe output side P1 of the pump P is the index drive motor 42, the ramstop actuating piston and cylinder assembly 53, the printing head pistonand cylinder actuating assembly 100, and the reverse motor means 91 foractuating the squeegee carriage means 70. Connected in series with theindex motor means 42 and in parallel with respect to each other is anormally opened deceleration valve 106 and a normally closed by-passvalve 107.

Operatively associated with a normally closed by-pass valve 107 is a ramstop lever 51 which is mechanically linked to the piston rod 53B of theram stop piston and cylinder actuating means 53. A solenoid actuatedcontrol valve means 108 is operatively connected to the ram stop pistonand cylinder assembly 55 to control the flow of fluid thereto andaccordingly the operation thereof.

A similar solenoid actuated valve 109 is operatively connected to theactuating piston and cylinder 100 to sequence the operation of theprinting head 60. Also a solenoid valve 110 is operatively connected tothe squeegee drive motor 91 to effect the proper sequencing of the motordrive so as to activate the squeegee and flood bars. The respectivesolenoid valves 108, 109 and 110 are of the type that are activated whena timed impulse is imparted thereto. The timing of the actuation of therespective solenoid valves 108, 109 and 110 to sequence the variousmachine operations is effected by a suitable timer operating a series ofcams for imparting a timed impulse to a switch means to operate therespective solenoid valves in accordance to a predetermined program.

Accordingly the operation of the machine is as follows:

In the non-printing position of the apparatus and in the at restposition, the printing head assembly 60 is normally in the raisedinoperative position as shown in the dotted or phantom line showing onFIG. 5. In this position of rest, the by-pass valve 107 is normallyclosed and the deceleration valve 106 is normally opened. The energizingof the electric motor 56 effects operation of the pump P to maintain afluid pressure on the system whereby the ram stop piston and cylinderassembly 55 holds the ram lever 51 in position A to prohibit indexing ofthe pallets, and the head activating piston and cylinder assembly 100holds the head frame 60 in the raised position. Upon an impulse orsignal generated by a suitable timer being imparted to the solenoidvalve 108 controlling the fluid flow to piston and cylinder assembly 53,the valve 108 is shifted causing the fluid to flow to chamber 53C toadvance the piston rod 53B. In doing so the ram lever 51 coupled theretois moved toward position B, causing the ram lever 51 to open the by-passvalve 107, thereby permitting the motor drive 42 to index the palletsabout the oval track 25. Upon rotation of the main drive shaft 40through a predetermined angular degree of rotation, the deceleration camcoupled thereto exerts an influence on the deceleration valve causingthe machine to decelerate as the pallets reach the respective succeedingstations.

With the pallets indexed, an impulse from a timer is supplied to thesolenoid valve 109 controlling the actuation of the head frameactivating piston and cylinder assembly 100 causing the head frame 60 tobe lowered into a printing position. As the printing head 60 is beinglowered to printing position the locating bars 35 coupled thereto aremoved into registration with the notches 34 of the respective pallets toinsure proper registration of the pallets relative to the screen 76, inthe printing position. As the printing head frame lowers, the printingscreen 76 supported thereon is moved into printing position over theworkpiece W supported on the pallet thereunder.

As the printing head 60 is being lowered, the carriage 71 is moved totransverse the flood stroke. As the head 60 reaches printing positionthe flood bar roller 81 engages the bridge member 82 causing the floodbar 77 to be moved out of engagement with the screen 76 supported on thescreen holder. When the head is lowered, the squeegee is engaged withthe screen in preparation to effecting the printing stroke. With thesqueegee in engagement with the printing screen, an impulse is impartedto the solenoid valve 110 to reverse the operation of the squeegee drivemotor 91 to traverse a printing stroke relative to the screen andthereby force the color through the screen and onto the workpiece W.

Upon completion of the printing operation an impulse is again impartedto the solenoid 109 controlling the head activated piston and cylinderassembly 100 to reverse the stroke of the piston causing the printinghead 60 to be raised to an inoperative position. Upon the initialmovement of the head frame 60 to the raised position, the squeegee 75 isfirst lifted off the screen 76, before the screen is lifted due to thelost motion resulting therebetween. Upon continued movement of the headframe to raised position, the lower stop 87B engages the screen holder85 causing the same to be raised with the head frame 60, the other endof the screen holder pivoting about pivot 88. As the printing head islifted, the flood roller 81 is raised off bridge member 82 causing thesprings 79 to bias the flood bar 77 toward the screen whereby a floodstroke is effected upon the return of the squeegee carriage 71 to itsinitial position upon a reversal of motor 91. With the printing head 60in the inoperative position the locating bars 35 are retracted or movedfree of the notches 34 whereby the pallets may be again indexed torepeat the cycle of operation.

From the foregoing it will be apparent that the number of palletsnecessary to effect a screen print on a series of independent articlesat optimum production speed is reduced to a minimum inasmuch as all ofthe pallets are disposed in a common plane whereby the various functionsof feeding, printing and removing of the printed article can be readilyachieved in a manner whereby all of the pallets can be effectivelyutilized as operating stations through the entire printing cycle of theapparatus. Therefore the number of pallets required to produce a givennumber of units per unit of time is at least half of that heretoforerequired to achieve the same or comparable production.

While the instant invention has been described with respect to aparticular embodiment thereof it will be readily understood andappreciated that variations and modifications of the invention may bemade without departing from the spirit and scope thereof.

What is claimed is:
 1. A screen printing machine comprisinga suportingframe means, an oval shaped rail mounted on said frame .Iadd.means,.Iaddend. a plurality of pallet means disposed in a common planecircumferentially spaced about said oval rail, drive means operativelyinterconnecting said pallet .Iadd.means .Iaddend.for indexing said.[.pallets.]. .Iadd.pallet means .Iaddend.about said oval rail in saidcommon plane, and .[.a.]. printing head means mounted on said framemeans for movement between an operative printing position and aninoperative non-printing position, .Iadd.said pallet means havingsubstantially coplanar movement as they approach, traverse and departsaid printing head means, .Iaddend.indexing means connected to saiddrive means for indexing said .[.pallets.]. .Iadd.pallet means.Iaddend.about said oval rail, said indexing means .[.including a.]..Iadd.includes .Iaddend.ram stop means, a ram stop cam followeroperatively associated with said drive means, .Iadd.and .Iaddend. .[.andan.]. activating means for moving said ram stop means into and out ofoperative position relative to said cam follower to effect the indexingof said .[.pallets.]. .Iadd.pallet means .Iaddend.about said oval rail.2. The invention as defined in claim 1 wherein said printing head meansincludes:a head frame pivotally mounted to said supporting frame means,a carriage movably mounted on said head frame, a squeegee means mountedon said carriage, a screen holder disposed below said carriage and.Iadd.said .Iaddend.squeegee means mounted thereon, said screen holderhaving one end pivotally mounted to said support frame means, and aconnecting link supporting the other end of said screen holder from saidhead frame, and means on said link connected end .Iadd.of said screenholder .Iaddend.for effecting a predetermined amount of lost motionbetween said head frame and carriage mounted thereon.[.,.]. and saidscreen holder as said printing head is pivoted between an operativeprinting position to an inoperative non-printing position.
 3. Theinvention as defined in claim 2 and including:a flood bar mounted onsaid carriage, means for normally biasing said flood bar towardoperative flooding position in the non-printing position of said headmeans, and means for overcoming said bias on said flood bar in theprinting position of said .Iadd.printing .Iaddend.head.
 4. The inventionas defined in claim 1 wherein said interconnecting drive means.[.including.]. .Iadd.includes .Iaddend.an endless flexible member, said.[.pallets.]. .Iadd.pallet means .Iaddend.being connected to saidendless flexible member at spaced intervals therealong, and .[.a.].means for effecting the drive of said endless flexible member.
 5. Theinvention as defined in claim 4 wherein said drive means comprises:adrive shaft having a driving sprocket connected thereto, said flexiblemember being threaded about said driving sprocket, .Iadd.and .Iaddend..[.a.]. motor means operatively connected to said drive shaft to effectthe drive thereof.
 6. A screen printing machine comprising:a supportingframe means, an oval shaped rail mounted on said frame, a plurality ofpallet means disposed in a common plane circumferentially spaced aboutsaid oval rail, means operatively interconnecting said pallet means forindexing said pallet means about said oval rail in said common plane, aprinting head means mounted on said frame means for movement between anoperative printing position and an inoperative non-printing position,.Iadd.said pallet means having substantially coplanar movement as theyapproach, traverse and depart said printing head means, .Iaddend. saidinterconnecting means including an endless flexible member, said palletmeans being connected to said endless flexible member at spacedintervals therealong, a drive means for effecting the drive of saidendless flexible member, .[.and.]. indexing means operatively connectedto said drive means for indexing said pallet means from station tostation about said oval rail, said indexing means including: .[.a.]. ramstop means, a ram stop cam follower operatively associated with saiddrive shaft to rotate therewith, .Iadd.and .Iaddend. .[.and.]. anactivating means for moving said ram .Iadd.stop .Iaddend.means.[.stop.]. into and out of operative position relative to said camfollower to effect the indexing of said pallet means about said ovalrail.
 7. The invention as defined in claim 4 and including registrationmeans operative to register said pallet .Iadd.means .Iaddend.in theprinting position.
 8. The invention as defined in claim 7 wherein saidregistration means are operatively associated with said printing head sothat said registration means are rendered operative when said.Iadd.printing .Iaddend.head is disposed in printing position.
 9. Ascreen printing machine comprising:a supporting frame, an oval shapedrail mounted on said supporting frame whereby the plane of said ovalrail is substantially horizontally disposed, a sprocket rotatablyjournalled adjacent each end of said oval shaped rail, an endlessflexible driving chain threaded about said sprocket, a plurality ofpallets connected to said chain at spaced intervals therealong, guiderollers connected to each of said pallets, .[.said.]. .Iadd. said.Iaddend.guide means being disposed in rolling engagement with said ovalrail, .[.a.]. drive means operatively connected to one of said sprocketsto effect the drive thereof, whereby said pallets are moved in a commonplane about said oval rail, indexing means operatively associated withsaid drive means for indexing said pallets about said oval track, saidindexing means including .[.a.]. ram stop means, a ram stop cam followeroperatively associated with said drive means, .Iadd.and .Iaddend. .[.andan.]. activating means for moving said ram stop means into and out ofoperative position relative to said cam follower to effect the indexingof said pallets about said oval rail, a printing head assembly mountedon said supporting frame for .[.moving.]. .Iadd.movement.Iaddend.between an operative printing position and an inoperativenon-printing position, .Iadd.said pallet means having substantiallycoplanar movement as they approach, traverse and depart said printinghead means, .Iaddend..[.and.]. .[.a.]. registration means operativelyassociated with said printing head means, .Iadd.and .Iaddend. saidregistration means operating on said pallets to effect accurateregistration of said pallets with said printing head assembly in theoperative printing position thereof.
 10. A screen printing machinecomprising:a supporting frame means, an oval rail mounted on said framemeans whereby the plane of said oval rail is substantially horizontallydisposed, a sprocket rotatably journalled on said supporting frameadjacent each end of said oval rail, an endless flexible driving chainthreaded about said sprocket, a plurality of pallets connected to saidchain at spaced intervals thereabout, said pallet having a locatingmeans on one end thereof, guide rollers connected to each of saidpallets, said guide rollers being disposed in rolling engagement withsaid rail, .[.a.]. drive means including: a drive shaft connected to oneof said sprockets, a motor means having an output shaft, a secondsprocket mounted on said drive shaft, a flexible driving member couplingsaid motor shaft to said second sprocket to effect the drive of saiddrive shaft when said motor means is activated, .[.an.]. indexing meansincluding: a ram stop cam follower connected to said second sprocket, aram stop pivotally mounted on said frame for movement into and out ofengagement relative to said cam follower, .[.a.]. ram stop activatingmeans operatively connected to said ram stop to effect actuation of saidram stop, means responsive to the actuation of said ram stop foreffecting the actuation of said motor means, a printing head assemblymounted on said frame for movement between a printing and non-printingposition, said printing head assembly including a head frame pivotallymounted on said support frame means, said head frame including opposedside rails, a carriage mounted on said side rails, a carriage drivemeans for traversing said carriage along said side rails, a squeegeemeans supported on said carriage, a screen holder adapted to support aprinting screen disposed below said squeegee, said screen holder beingpivotally mounted to said supporting frame means adjacent one endthereof, an interconnecting link .[.supporting.]. .Iadd.supportinglyconnecting .Iaddend.the other end of said screen holder to said headframe, said interconnecting link including means for effecting apredetermined amount of lost motion between said head frame and saidscreen holder as said printing head assembly moves between a printingand non-printing position, .[.and a.]. registration means for accuratelypositioning said pallet in the printing position, said registrationmeans including a locating bar pivotally mounted on said supportingframe, .Iadd.and .Iaddend. .[.and a.]. linkage means interconnectingsaid locating bar to said head frame whereby said locating bar is movedinto registration with the locating means of said pallet in the printingposition of said head assembly and out of registration with the locatingmeans of said pallet in the non-printing position of said head assembly.11. The invention as defined in claim 10 and includinga flood .Iadd.bar.Iaddend.movably mounted on said carriage, .[.a.]. spring means fornormally biasing said flood bar toward .[.a.]. .Iadd.said.Iaddend.printing screen, .Iadd.and .Iaddend. .[.and.]. meansoperatively connected to said flood bar for overcoming the bias of saidspring in the printing position of said .Iadd.printing .Iaddend.headassembly.
 12. The invention as defined in claim 11 wherein said lattermeans .Iadd.includes .Iaddend..[.includes.]. a flood roller connected tosaid flood bar, a flood bar bridge supported below said head side rails,.Iadd.and .Iaddend. said flood roller being disposed in rollingengagement with said bridge in the printing position of said headassembly for maintaining the associated flood bar off the printingscreen in the printing position. .Iadd.
 13. A screen printing machinefor textile materials comprising: a supporting frame, a rail having apredetermined peripheral geometric configuration, a plurality of palletmeans disposed in a substantially common plane and spaced in apredetermined manner about the periphery of said rail, said pallet meansbeing capable of having textile workpieces positionally disposedthereon, drive means including indexing means operativelyinterconnecting said pallet means for repeated automatic movement ofsaid pallet means about said rail in said common plane and in only asingle predetermined direction during a given printing sequence, saidindexing means moving said pallet means by predetermined distances suchthat when said pallet means is disposed at a printing station it is inproper position for printing without any further additional indexingmovement, printing head means for multicolored printing upon saidtextile workpieces being mounted on said supporting frame for movementbetween an operative printing position and an inoperative non-printingposition, and said pallet means having substantially coplanar movementas they approach, traverse and depart said printing means..Iaddend..Iadd.
 14. A screen printing machine in accordance with claim 13,wherein said indexing means includes ram stop means, a ram stop camfollower operatively associated with said drive means, and activatingmeans for moving said ram stop means into and out of operative positionrelative to said cam follower to effect the indexing of said palletmeans about said rail. .Iaddend..Iadd.
 15. A screen printing machine inaccordance with claim 13, wherein said pallet means are spaced from oneanother to define a plurality of spaced stations, said indexing meansoperatively indexing said pallet means from station to station about theperiphery of said rail, and registration means operable to register saidpallet means in the printing position. .Iaddend. .Iadd.
 16. A screenprinting machine in accordance with claim 15, wherein said registrationmeans are operable subsequent to said indexing means. .Iaddend..Iadd.17. A screen printing machine in accordance with claim 15, wherein saidregistration means is operatively interconnected between said supportingframe and said pallet means. .Iaddend..Iadd.
 18. A screen printingmachine in accordance with claim 15, wherein said registration means isoperatively associated with said printing head means so as to rendersaid registration means operative when said printing means is disposedin the printing position. .Iaddend..Iadd.
 19. A screen printing machinein accordance with claim 13, wherein said rail includes at least oneperipheral portion having an arcuate traverse path. .Iaddend. .Iadd. 20.A screen printing machine in accordance with claim 19, wherein theperipheral end portions of said rail are of an arcuate configuration..Iaddend..Iadd.
 21. A screen printing machine in accordance with claim17, wherein said registration means includes a locating member movablymounted on said supporting frame, said registration means also includinglocating means formed in said pallet means, and said locating memberbeing movable into registry with said locating means to effectregistration of said pallet means. .Iaddend. .Iadd.
 22. A screenprinting machine in accordance with claim 21, wherein said locatingmember is movable into registry with said locating means in the printingposition of said printing head means and out of registry with saidlocating means in the non-printing position of said printing head means..Iaddend..Iadd.
 23. A screen printing machine in accordance with claim22, wherein said locating member comprises a locating bar pivotallymounted on said supporting frame. .Iaddend..Iadd.
 24. A screen printingmachine in accordance with claim 23, wherein said locating meanscomprises a notch of predetermined configuration formed at one end ofsaid pallet means and disposed on the underside thereof. .Iaddend..Iadd.
 25. A screen printing machine in accordance with claim 22,including linkage means interconnecting said locating member and saidprinting head means. .Iaddend.